Detergent composition and method



Patented Oct. 10, 1944 UNITED FEE DETERGENT COMPOSITION AND METHOD NoDrawing. Application May 4, 1942, Serial No. 441,664

13 Claims.

This invention relates to a detergent composition and method, and moreparticularly to a detergefit composition having the property ofcontrolling foaming and inhibiting gelling in commercial detergentsolutions employed in the Washing of bottles and the like.

In washing machines for washing bottles, pans, and the like. andparticularly in dairy and baking equipment, detergent solutions areemployed in the automatic or machine washers. The detergent solutionnormally employed is a strong caustic or highly alkaline solution. Inany operation of this nature in which the articles to be washed arecontaminated with saponifiable fatty matter, as is the case in dairy andbakery equipment, the fats become saponified during the washingoperation to form sodium soaps by reaction with the caustic. Thepresence of the soap causes the solution to foam, the foam frequentlyoccurring to such an extent as to overflow the washing machine tank.Furthermore it is the practice to continue to use the detergentsolutions until they have become exhausted. During the use the soapsbuild up to such an extent that upon shutting down the machine for thenight, the solution solidifies to a stiff gel. The difficulty ofredissolving the gel is such that the solution is discarded long beforeit has ceased to be effective as a cleaner.

It has heretofore been suggested to use commercial anti-foaming agents,but those heretofore known have been insoluble in the solution, haveonly a very temporary effect, and have no effect upon the gelling of thesoaps. Furthermore anti-foaming agents heretofore known, beinginsoluble, contaminated the articles being Washed, generally by an oilyfilm which remained on the washed article.

It has now been discovered that effective foaming control may besupplied, without the disadvantages of the previous foaming controlagents, and at the same time gelling may be materially inhibited so thatthe detergent solution may be ut lized for greatly increased periods.This control may be accomplished by the use of water soluble alkalimetal salts of the alkyl esters of phosphoric acids. The preferred alkylgroup is the octyl group. The preferred phosphoric acid isorthophosphoric acid. Other alkyl groups may, however, be employed suchas the amyl. and the capryl, although these esters are markedly inferiorto the octyl ester. The molecularly dehydrated phosphoric acids maylikewise be employed, such as pyrophosphoric, metaphosphoric andpolyphosphoric acids.

The compounds herein described'as foaming and gelling inhibitors arealso effective wetting agents and increase the cleaning efficiency ofthe detergent solutions.

Anti-foaming and anti-gelling control may be accomplished simply byadding a small amount of the acid octyl phosphate to a solution of anyof the well known commercial alkaline detergents which include causticsoda.

As an example of the effect of the phosphates on foaming, a solution wasprepared containing 3% caustic soda, 1.5% sodium carbonate, 0.025%linseed fatty acid, and the balance water. To one sample of thismaterial 0.12% of mono-octyl orthophosphate was added and compared withan identical solution to which the phosphate had not been added. In eachcase four liters of the solution were placed in a 10" diameter glasscylinder and agitated by means of a circulating pump, withdrawingsolution from the bottom of the cylinder and discharging into the top ofthe cylinder about 10 above the liquid level. A temperature ofapproximately 140 F. was maintained, this being approximately thetemperature of commercial solutions. The solution containing thephosphate was continuously circulated for three days, during which timethe foam did not rise higher than 1" above the liquid level and it wasgenerally considerably lower than that. The solution which did notcontain the octyl phosphate produced a foam which rose to a height of10" and then overfiowed the cylinder, within less than 10 minutes fromthe start of the circulation.

In a comparative test, using the same solution without the octylorthophosphate, attempts were made to control the foam by theapplication of known foam inhibitors, for example of the tributylphosphate type. These inhibitors broke the foam but their operation'wasonly temporary and it was necessary to add new amounts of theseinhibitors every few hours. The tributyl phosphate formed an oily filmon the liquid.

In another test a solution was prepared containing 3% caustic soda and0.05% linseed fatty acid. In the control. without the addition of theoctyl phosphate, the foam rose to 10" and then overflowed the cylinderwithin 5 minutes. The addition of 0.08% of mono-octyl orthophosphate tothe foaming solution produced a subsidence of tially the same totalproportion, and the results were substantially the same.

Another aqueous test was made by employing a solution containing 3%caustic soda, 3% sodium carbonate, and 0.025% of a commercial foamingagent of the alkyl aryl sulfonate type. The foam was controlled by theaddition of 0.25% sodium octyl orthophosphate so that during 36 hours ofagitation the foam did not exceed 1.5" in height.

The foregoing tests were concerned only with foaming control. Anadditional series of tests on gelling control or inhibition areindicative of the value of the materials for that purpose.

For example a butterfat soap composition was prepared by melting 116.5grams of butter and adding 32 grams of a 50% caustic soda solution. Themixture was heated and agitated for several hours until a thick soappaste formed. The mixture was continuously stirred and cooled and ascooling progressed the soap congealed in the form of granules includingall of the products of the saponiflcation reaction. The solution of thiscomposition in a normal caustic detergent is, so far as has beenascertained, equivalent to the saponiflcation which takes place in thewashing of milk containers.

Test solutions of the soap paste so prepared were made by dissolving thepaste in duplicate proportions of a 3% caustic soda solution which wasmaintained at 140 F. In each test one of the portions was used as ablank. In the other portion 0.5% of mono octyl sodium orthophosphate wasadded to the solution.

The solutions were allowed to cool overnight at room temperature andtheir gelling characteristics noted. In the control solutions gellingoccurred at butter soap concentrations of less than 0.025%, and at aconcentration of 0.10% a semi-solid gel set up. This gel became solid atconcentrations of 0.25%.

In the other set of samples containing mono octyl sodium orthophosphateno gelling was noted below 0.25% butter soap concentration and a solidgel did not occur until a concentration of 0.5% butter soap was reached.Furthermore an uninhibited solution containing 0.25% butter soap, whichhad set up to a solid gel, did not clear up on reheating even forseveral hours, whereas the solid gel in the inhibited solutionredissolved easily to a clear solution upon heating.

Other water soluble alkali metal salts of alkyl phosphate esters,particularly those containing more than four carbon atoms in the alkylgroup are partially efiective as foam inhibitors but are not aseffective commercially as the octyl esters.

In general the ester salts of pyro and polyphosphoric acids, such as theoctyl salts are satisfactory inhibitors but are not quite as stable asthe orthophosphate ester. For example, 5 grams of dioctyl sodiumpyrophosphate were added to 4 liters of a foaming solution containthedioctyl sodium pyrophosphate stabilized the foam at a height of 1.5 to2.5" during an 8-hour test period at 140 F. In commercial practice it ispreferred to introduce the foaming and gelling inhibitor into theinitial detergent composition.

A fused mixture of caustic soda and acid octyl phosphate in the desiredproportions to give an anti-foaming and anti-gelling solution, whendissolved in water to yield a caustic concentration of 0.25% to 10%,provides a suitable commercial mixture, but is somewhat tacky andbygroscopic. The preferred commercial composition is non-hygroscopic andgranular and may be prepared by mixing acid octyl phosphate with sodaash. For example 10 to parts of mono octyl orthophosphate in paste formmay be thoroughly admixed with 90 to 50 parts of soda ash to give a drygranular product. This product may then be dissolved in water with otheralkaline agents such as caustic soda.

In all cases the acid ester may be employed or the ester salt. When theacid ester is employed it is neutralized by the soda ash or causticalkali.

In most detergent operations, both foam and gel control are essential,but in some cases where little or no saponiiiable matter is present,foam control alone is important. Concentrations of the octyl typeinhibitor as low as 0.05% are effective for foam control in most alkalisolutions. For gel control, concentrations of at least 0.25% aredesirable. In either case concentrations above 1.0% do not increase theeffectiveness of control either of foaming or gelling but the higherconcentrations are not detrimental.

While the caustic soda concentration in the detergent solutions mayrange from 0.25% to 10%, it is preferred to use a 1% to 4% concentrationof caustic soda for most commercial washing operations.

The use of sodium carbonate with the octyl sodium phosphate in causticsoda solutions increases the efllciency of foam control, improves thewetting power and the cleaning efliciency of the solution. The amount ofoctyl sodium phosphate required for effective foam control in a solutioncontaining 3% NaOH and 3% NazCO: is only about half of that requiredwhere the sodium carbonate is absent. Ordinarily the amount of soda ashemployed is from 2 to 10 times the amount of octyl sodium phosphate,inasmuch as a satisfactory commercial preparation of dry nonhygroscopiccharacter can be prepared from mixtures of these two components withinthat range. The soda ash-octyl sodium phosphate composition may be usedalone as a detergent composition but the caustic soda increases theeffectiveness of the foam control.

The foregoing detailed description has been given for cleamess ofunderstanding only, and

no unnecessary limitations should be understood therefrom.

What we claim as new, and desire to secure by Letters Patent, is:

1. An anti-foaming and anti-gelling detergent solution for use inautomatic washing equipment for bottles, pans and the like, comprisingwater, from 0.25% to 10% by weight of the solution of caustic soda, andfrom 0.05% to approximately 1% by weight of a water soluble sodium saltof an octyl ester of a phosphoric acid as a foaming and gellinginhibitor.

2. A product as set forth in claim 1, in which the ester is dioctylsodium pyrophosphate.

3. An alkaline'detergent composition for use in automatic washingequipment for bottles, pans and the like, comprising a mixture of 10 to50 parts by weight of mono octyl orthophosphate and to 50 parts byweight of soda ash.

4. An anti-foaming and'anti-gelling detergent v I I solution for use inautomatic washing equipment for bottles, pans, and the like, comprisingwater, from 0.25% to 10% by weight of the solution of caustic soda, from0.1% to 10% by weight of sodium carbonate, and from 0.051% toapproximately 1% by weight of a water soluble sodium salt of an octylester of a phosphoric acid as a forming and gelling inhibitor.

5. A product as set forth in claim 4, in which the ester is mono octylsodium orthophosphate.

6. An alkaline detergent composition for use in automatic washingequipment for bottles, pans, and the like, comprising a fused mixture ofcaustic soda and acid octyl phosphate in proportions to provide ananti-foaming and anti-gelling solution when dissolved in water to yielda caustic concentration of 0.25% to 10% by weight.

7. The method of cleaning bottles, pans and the like in automaticwashing equipment which comprises washing such an article in a 0.25% to10% caustic alkali solution to which has been added an amount of watersoluble alkali metal salt of an alkyl ester of a phosphoric acid insumcient quantity to inhibit'foaming and gelling of saponified matter asit forms in the washing operation, the proportion of ester being from0.05% to approximately 1% by weight of the solution.

8. The method as set forth in claim 7 in which the ester is an octylester.

9. The method as set forth in claim 7 in which the ester is an octylester of orthophosphoric acid.

10. A solution as set forth in claim 1 in which the proportion ofcaustic soda is from 1% to 4% and the ester is approximately 0.25%

11. A solution as set forth in claim 4 in which the caustic soda is from1% to 4%, the octyl ester is approximately 0.25% and the sodiumcarbonate is approximately 3%.

12. A solution as set forth in claim 1 in which the caustic soda is from1% to 4%.

13. A solution as set forth in claim 4 in which 20 the caustic soda isfrom 1% to 4%.

HARRY H. HULL.

LEWIS SHERE.

